The present invention relates to signaling protocols in telecommunications networks (e.g., mobile networks). More particularly, the present invention relates to a telecommunications network signaling protocol that is independent of the underlying signaling bearer service.
Typically, networking systems employ what is known in the art as a layered architecture. In a layered architecture, data and/or signaling messages are transferred between peer entities on the same level of the layered architecture with the help of the services provided by the underlying layers. The messages exchanged between the peer entities are generated, formatted, transmitted, received and transported according to the rules described in a protocol specification. The functionality provided by an underlying layer for the layer above it, as well as the formatting and coding of the information that is exchanged between adjacent layers are described in an interface specification. An interface specification usually describes each function provided by the underlying layer in terms of a corresponding service primitive, wherein each primitive is associated with a particular function or service provided by the underlying layer for the layer just above it. Information exchanged between the layers is described in terms of parameters of a particular primitive.
A simple layered architecture may, from top to bottom, include an application layer, a network layer, a data link layer and a physical layer. The function of the application layer is to generate, process and format data and/or signaling that is required to support a particular user application (e.g., a cellular voice service). The function of the network layer is to manage the links and end-to-end relationships between the various network entities, for example, the various mobile switching centers, radio network controllers, and base station units in the cellular network. The data link layer provides means (i.e., links) for assured mode transfer of data and signaling between adjacent nodes in the network. The physical layer provides services which are required to interface with the physical environment, such as encoding, modulating, transmitting and receiving signals.
It will be understood that the layered architecture described above may include a signaling layer, wherein the signaling layer is actually part of the application layer or the network layer. The signaling layer, as the name suggests, generates and receives signaling messages, in accordance with a particular signaling protocol (e.g., Q.2931, PNNI, and B-ISUP). The signaling protocol provides the rules which govern the generation and format of the signaling messages. The signaling messages, in turn, are used, for example, to set-up maintain and release connections between network entities.
It will also be understood that a lower-layer network service, such as a signaling bearer service, is required to transport the signaling messages from a sending entity to a receiving entity. Examples of signaling bearer services include the Signaling ATM Adaptation Layerxe2x80x94User Network Interface (SAAL_UNI) service and the Message Transfer Part 3 (MTP3) service. Generally, in a layered architecture, the signaling bearer service is associated with the functional layers below the signaling layer.
Typically, different networks employ different signaling bearer services. In addition, signaling protocols are designed such that they are compatible with a particular signaling bearer service. For example, the ITU UNI signaling protocol (Q.2931) is designed such that it must be carried by the Signaling ATM Adaption Layerxe2x80x94User Network Interface (SAAL_UNI) signaling bearer service. Likewise, the Private Network-Network Interface (PNNI) signaling protocol must be carried by the SAAL_UNI signaling bearer service. However, the Broadbandxe2x80x94Integrated Services Digital Network (B-ISDN) User Part (B-ISUP) signaling protocol is designed such that it must be carried by the Message Transfer Part (MTP3) bearer service associated with the Signaling System Seven (SS7). As telecommunications networks continue to overlap, interconnect and share services with each other, utilizing a signaling protocol that is incompatible with all but one signaling bearer service will become more problematic because it may restrict a user""s access to and coverage within certain networks. It would, therefore, be highly desirable to have a signaling protocol that can generate, process and receive signaling messages independent of the underlying signaling bearer service.
It is an object of the present invention to provide a more flexible signaling protocol architecture.
It is an object of the present invention to provide a telecommunications network signaling protocol that is capable of generating signaling messages independent of the underlying signaling bearer service that is being used to transport the signaling messages.
It is an object of the present invention to provide a signaling protocol that can be used in conjunction with different telecommunications applications, networks, network segments, and markets, without having to first modify the signaling protocol.
The Asynchronous Transfer Mode, Adaptation Layer 2 (AAL2) is a well known mechanism that can be used for transferring data and signaling information, as described in ITU-T Recommendation No. I.363.2, xe2x80x9cB-ISDN ATM Adaptation Layer Type 2 Specification,xe2x80x9d September 1997. It is expected that AAL2 will soon be widely used in conjunction with different telecommunications applications, networks and markets.
In general, the present invention involves an AAL2 signaling protocol that can now be employed regardless of the underlying signaling bearer service that is used for setting-up, maintaining and tearing-down end-to-end AAL2 connections. This is achieved by dividing the functionality of the AAL2 signaling protocol into a number of functional sublayers: an AAL2 Signaling Common Part (ACP), a Bearer Coordination Part (BCP) and a Bearer Adaptor Part (BAP), wherein the BCP makes it possible to dynamically switch between different signaling bearer services. The functions performed by each of these layers will be described in more detail below.
In accordance with one aspect of the present invention, the above-identified and other objects are achieved by a method for generating signaling messages in accordance with a signaling protocol that is independent of an underlying signaling bearer service. The method involves generating a signaling message independent of the underlying signaling bearer service to be used in transporting the message to a remote network node, then invoking a service primitive, wherein the signaling message is a parameter in the service primitive. The method then involves adapting the service primitive so that it is compatible with the underlying signaling bearer service.
In accordance with another aspect of the present invention, the above-identified and other objects are achieved by a method for receiving signaling messages in accordance with a signaling protocol independent of an underlying signaling bearer service. This method involves receiving an incoming message at a local network node, independent of the underlying signaling bearer service used to transport the incoming message from a remote network node, wherein the incoming message is a parameter in an incoming service primitive. The method also involves adapting the incoming service primitive from a format that is compatible with the underlying signaling bearer service to a format that is compatible with the signaling protocol.
In accordance with another aspect of the present invention, the above-identified and other objects are achieved by an apparatus for generating signaling messages that employs an AAL2 signaling protocol that is independent of an underlying signaling bearer service. The apparatus includes means for generating a message independent of the underlying signaling bearer service to be used in transporting the message to a remote network node, and means for invoking a service primitive, wherein the signaling message is a parameter in the service primitive. The apparatus also includes bearer adaptation means for converting the service primitive from a format that is compatible with the AAL2 signaling protocol to a format that is compatible with the underlying signaling bearer service.
In accordance with another aspect of the present invention, the above-identified and other objects are achieved by an apparatus for receiving signaling messages that employs an AAL2 signaling protocol independent of an underlying signaling bearer service. The apparatus includes means for receiving an incoming message independent of the underlying signaling bearer service, which is employed to transport the incoming message from a remote network node to a local network node, wherein the incoming message is a parameter in an incoming service primitive. The apparatus also includes bearer adaptation means for adjusting the service primitive from a format that is compatible with the underlying signaling bearer service to a format that is compatible with the AAL2 signaling protocol.